Software upgrade for redundant pair of Mediant 800B, enabling 50 SIP registrations on each E-SBC. This is needed to support remote worker and NAT Traversal and Survivability (for IP-Centrex, Remote Branch Office and Disaster Recovery) during WAN failure. For maximal capacity refer to release notes. Valid in combination with existing/new E-SBC license only. Can be ordered in multiple quantities up to the maximal described capacity. Can only be used with Mediant 800B that were initially ordered as redundant pair - M800B-ESBC/R.